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(No Model.) 2 Sheets-Sheet 1.

L. STEVENS.

FURNACE FOR STEAM BOILERS.

Patented Dec. 29, 1885.

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No. 333,430. Patented Dec. 29, 1885.

UNITED STATES PATENT Gr mes.

LEVI STEVENS, OF \VASHINGTON, DISTRICT OF COLUMBIA.

FURNACE FOR STEAM-BOILERS.

El-PECIFICATION forming part of Letters Patent No. 333,430, dated December 29, 1885.

Application filed August 10, 1885. Serial No. 17 ,961. (No model.) i

To all whom it may concern:

Be it known that I, LEVI STEVENS, of Washington city, in the District of Columbia, have invented a new and useful Improvement in 5 Furnaces for Steam-Boilers; and I do hereby declare that the following is a full and exact description thereof, reference being had to the accompanying drawings, and tothe letters of reference marked thereon, making a part of this specification.

Myinvention relates to improvements in the furnaces of steam-boilers, and has for its'object to obtain a perfect combustion under the boiler of the fuel and of the gases evolved therefrom, and at the same time to so equalize and diffuse the heat over the surface of the boiler as to prevent injury thereto from the effects of a too intense heat at any one point.

In the accompanying drawings, Figure 1 is a longitudinal central section through my improved furnace and its combustion-chambers, the boiler over the furnace being shown in elevation; Fig. 2, a transverse section looking toward the rear in line a; x of Fig. 1; Fig. 3, a similar section in line y y of Fig. 1; and Fig. 4:, a view in perspective from the front of the improved furnace, portions of its walls being broken away to illustrate its details of construction.

A represents a tubular boiler supported in the customary manner upon the walls of the furnace.

O is the fire-box,fitted with grate-bars D D, over an ash-pit, E. The top and sides of the fire-box G are inclosed by an-arch, F, and at its inner end a hot-air chamber, G, is partitioned off by a bridge-wall, G, and covered by tiles or a metallic plate, a, so as to leave a flue or space, H, between said covering-plate and the arched top of the fire-box, as shown in Fig. l. A superheater, I, properly supplied with steam from the boiler, is fitted upon the top of the hot-air chamber G, so as to be exposed to the direct heat from the fire-box. The discharge-pipe 1 from the superheater is led to the ash-pit and fitted to deliver a jet of highly-heated steam under the grate-bars in conjunction with the supply of air delivered into the ash-pit in the usual manner through the front draft doors or openings, or by artificial blast from a blower when the natural draft is insufficient. The hot-air chamber G is supplied with air from the ash-pit through a series of openings, mm,- in the bottom of the chamber, controlled by a sliding valve, m. This valve m serves also to regulate the amount of air delivered from said chamber G by determining the supply thereto. The front wall, G, of this chamber G serves,at the rear of the fire-box, to divert upward the outflowing currents formed therein by the gases and products of combustion. A series of small openings, a n, are pierced through this wall near to the top thereof, to communicate directly with the fire-box at the point where the hot gases flow up over the wall, so that a minutely-divided supply of air drawn from the ash-pit and highly heated in the chamber G is admitted to the gases at this point to perfect and intensify their combustion.- That portion of the arch of the firebox immediately above the hotair chamber G is pierced with a series of openings, r r 1", through which the products of combustion from the firebox O, mingled with the jets of air admitted through the openings a n from the chamber G, are allowed to flow in divided streams underthe boiler. The rear wall, a, of the fire-box, over the hot-air chamber G, is in like manner perforated to furnish a sufiicient area of dis'charge-open- 8o ings, and yet produce a minute subdivision of the intensely hot currents as they issue from the fire-box. A second wall, R, is built at a short distance back of the rear wall of the fire-box and. hot-air chamber to form a partition immediately under the boiler, which shall serve to arrest and check the hot currents rushing back from the apertures a n in the arch and rear wall of the fire-box. A second combustion-chamber, T, is thus obtained, in which the products of combustion are detained and subjected-to a second charge of highly-heated atmospheric air admitted in finely-divided jets through a series ofsmall openings, 8 s, in the rear wall of the chamber G, near the top thereof, so as to strike immediately under the volume of gases inflowing from the fire-box O. The fresh hot air is thus made to mingle with and act quickly upon the hot gases, which, after a momentary check and detention in this combustion-chamber T, are again subdivided into numerous currents and submitted to contact with highly-heated surfaces by being made to pass through a series of perforations,

t t, in the second wall, R. The effect of the perforated arch F, separating the fire-box C from the boiler A, is to distribute the burning gases and perfect their combustion by facilitat- "ing [thej introduction of hot air thereto, and

by causing them to pass through a series of intensely hot flues such as are presented by the openings rr rin or between the bricks of the arch, and this object is further attained by the combination, with this cellular or perforated arch arranged as described, of the second combustion-chamber, T, into which a fresh supply of hot air is admitted, and of the second cellular or perforated wall, B, through whose heated openings t t t the gases are again carried. By this construction of the furnace a sufficient amount of oxygen is admitted to produce perfect combustion, while so high a temperature is constantly maintained by means of the passages in the brick walls, through which the gaseous currents are made to pass, as to produce a complete consumption of the carbon, and thereby wholly prevent all smoke from the furnace. At the same time the heat is so distributed over the exposed surface of the boiler as that the latter may not be injured thereby.

I claim as my invention- 1. The combination, with a furnace or firechamber inclosed at top and sides by a perforated arch, of a hollow bridge-wall at the rear of the furnace inclosiug a hot-air chamber communicating with the ash-pit below and the fire-chamber above and a perforated rear wall built upon the back end of the bridge to close the opening above it, substantially in the manner and for the purpose herein set forth.

2. The combination, with an inclosed furnace or fire-chamber constructed with a hollow rear bridge-wall inclosing a hot'air cham- 40 her made to communicate with the fire-chamber through small apertures in the upper portion of the wall, of a discharge flue or passage for the products of combustion formed between the top of the bridge-wall and the arch of the fire-chamber and terminating in a series of openings pierced through the arch and the rear wall over the bridge-wall, sub stantially in the manner and for the purpose herein set forth. 5o

3. The cellular or perforated arch F, bars D, and ash pit E, in combination with a hollow bridge-wall, G, and perforated rear wall, 0, substantially in the manner and for the pur pose herein set forth.

4. The combination,with a boiler, and with a firechamber under the boiler constructed with an arched top pierced with a series of openings at the rear end thereof, and with'a rear wall pierced with a series of openings in the upper portion thereof, of a second combastion-chamber under the boiler and back of the fire-chamber communicating by a series of small air-ports with a hot-air chamber,and whose rear wall is constructed with its upper portion solid and its lower portion pierced with a series of discharge'openings, all sub stantially in the manner and for the purpose herein set forth.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

LEVI STEVENS.

Vitnesses:

O. A. SHAW, L. J. \VHITE. 

